1. Technical Field
The present invention relates to a video display process and device such as a monitor for a computer system, and, more particularly, to a video control circuit for a video display device for controlling gains of red(R), green(G), and blue(B) color video signals, brightness and contrast for a video display, and bias of a color video signal.
2. Related Art
In general, a monitor controls a white balance by varying gains of R, G, and B color video signals inputted from a computer system, and controls contrast to distinctly show light and dark sides of a video display.
Further, a cathode ray tube which is used for a monitor requires a specific range of brightness values. A cutoff voltage of the cathode ray tube is determined according to biases of R, G, and B color video signals which are displayed on the cathode ray tube, and brightness varies when a bias voltage occurs based on the determined cutoff voltage according to control of the brightness.
Exemplars of designs in the art include those shown by U.S. Pat. No. 5,432,566 to Tanaka et al., entitled Video Circuit Controlling Brightness And/Or Saturation, U.S. Pat. No. 5,386,247 to Shafer et al., entitled Video Display Having Progressively Dimmed Video Images And Constant Brightness Auxiliary Images, U.S. Pat. No. 5,367,231 to Kobayashi et al., entitled Display System, U.S. Patent No. 5,359,266 to Smith et al, entitled System For Generating Triggering Pulses For Use In Beam Indexing Type Color Cathode Ray Tubes, U.S. Pat. No. 5,107,189 to Page, entitled RGB Video Amplifier System Integrating Blanking And Brightness Control Tracking, U.S. Pat. No. 4,945,403 to Kubo et al., entitled Color Television Format Using Pulse Frequency And Pulse Width Modulation, and U.S. Pat. No. 4,213,144 to de Boer, entitled Method Of Modulating A Composite Color Television Signal On A Carrier Signal And Device For Carrying Out Said Method.
Typically, these video control circuits have control sections, each controlling gains of the R, G and B color video signals, the brightness, the contrast and bias. As discussed in more detail below however, such a conventional video control circuit must have a microcomputer which is quite expensive in nature, and which specifically has enough output terminals to control the gains of the R, G and B color video signals, the brightness, the contrast and the bias. This results in an increase in the production cost of such a microcomputer, as well as complication in the design of the printed circuit board on which the microcomputer is disposed.